Table saw with improved safety system

ABSTRACT

A table saw having an adjustable blade, a detection system to detect contact between a person and the blade, and a brake mechanism to engage and stop the blade upon detection of contact between the person and the blade is disclosed. The saw includes a brake positioning system that adjusts the position of the brake mechanism to maintain the brake mechanism in an operative position relative to the blade as the position of the blade is adjusted. The saw also may include a retraction system that urges the blade downward, away from a user, upon detection of contact between a person and the blade. The retraction system may include a releasable gear. The saw may be constructed so that the blade is adjustable up and down around a pivot point downstream of the blade relative to the feed direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional continuation of U.S. patent applicationSer. No. 09/929,235 filed Aug. 13, 2001, and issuing as U.S. Pat. No.7,350,444 on Apr. 1, 2008, which in turn claimed the benefit of andpriority from the following U.S. Provisional Patent Applications: Ser.No. 60/225,056, filed Aug. 14, 2000, Ser. No. 60/225,057, filed Aug. 14,2000, Ser. No. 60/225,058, filed Aug. 14, 2000, Ser. No. 60/225,059,filed Aug. 14, 2000, Ser. No. 60/225,089, filed Aug. 14, 2000, Ser. No.60/225,094, filed Aug. 14, 2000, Ser. No. 60/225,169, filed Aug. 14,2000, Ser. No. 60/225,170, filed Aug. 14, 2000, Ser. No. 60/225,200,filed Aug. 14, 2000, Ser. No. 60/225,201, filed Aug. 14, 2000, Ser. No.60/225,206, filed Aug. 14, 2000, Ser. No. 60/225,210, filed Aug. 14,2000, Ser. No. 60/225,211, filed Aug. 14, 2000, and Ser. No. 60/225,212,filed Aug. 14, 2000. The disclosures of all these applications arehereby incorporated by reference in their entireties.

FIELD

The present invention relates to table saws and more particularly to atable saw with an improved safety system.

BACKGROUND

Table saws are a type of woodworking machinery used to cut workpieces ofwood, plastic and other materials. Table saws include a flat surface ortable with a circular saw blade extending up through a slot in thetable. A user slides a workpiece on the table against and past the bladewhile the blade is spinning to cut the workpiece.

Of all the tools in a wood working shop, table saws present perhaps thegreatest risk of injury. Table saws present a risk of injury to usersbecause the spinning blade is often exposed when in use. The blade cutsvery quickly and can sever a finger upon the slightest slip ormisplacement. Accordingly, safety features or systems have beendeveloped to minimize the risk of injury. Probably the most commonsafety feature is a blade guard that physically blocks a user frommaking contact with the spinning blade. In many cases, blade guardseffectively reduce the risk of injury, however, there are many instanceswhere the nature of the operations to be performed precludes using aguard that completely blocks access to the blade. There exists a needfor a table saw with a safety system that significantly reduces the riskof serious injury from a user accidentally contacting the spinningblade.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a machine with a fast-actingsafety system.

FIG. 2 is a schematic diagram of an exemplary safety system in thecontext of a machine having a circular blade.

FIG. 3 shows a table saw.

FIG. 4 is a schematic side view of one side of a table saw with animproved safety system.

FIG. 5 is a schematic side view of a second side of the table saw ofFIG. 4.

FIG. 6 is a schematic bottom view of the table saw of FIG. 4.

FIG. 7 is a schematic perspective view of the table saw of FIG. 4.

DETAILED DESCRIPTION

Machine 10 may be any of a variety of different table saws. Machine 10includes an operative structure 12 having a cutting tool 14 and a motorassembly 16 adapted to drive the cutting tool. Machine 10 also includesa safety system 18 configured to minimize the potential of a seriousinjury to a person using machine 10. Safety system 18 is adapted todetect the occurrence of one or more dangerous conditions during use ofmachine 10. If such a dangerous condition is detected, safety system 18is adapted to engage operative structure 12 to limit any injury to theuser caused by the dangerous condition.

Machine 10 also includes a suitable power source 20 to provide power tooperative structure 12 and safety system 18. Power source 20 may be anexternal power source such as line current, or an internal power sourcesuch as a battery. Alternatively, power source 20 may include acombination of both external and internal power sources. Furthermore,power source 20 may include two or more separate power sources, eachadapted to power different portions of machine 10.

It will be appreciated that operative structure 12 may take any one ofmany different forms, depending on the type of machine 10. For example,operative structure 12 may include a stationary housing configured tosupport motor assembly 16 in driving engagement with cutting tool 14.Alternatively, operative structure 12 may include a movable structureconfigured to carry cutting tool 14 between multiple operatingpositions. As a further alternative, operative structure 12 may includeone or more transport mechanisms adapted to convey a workpiece towardand/or away from cutting tool 14.

Motor assembly 16 includes one or more motors adapted to drive cuttingtool 14. The motors may be either directly or indirectly coupled to thecutting tool, and may also be adapted to drive workpiece transportmechanisms. Cutting tool 14 typically includes one or more blades orother suitable cutting implements that are adapted to cut or removeportions from the workpieces. The particular form of cutting tool 14will vary depending upon the various embodiments of machine 10. Forexample, in table saws, miter saws, circular saws and radial arm saws,cutting tool 14 will typically include one or more circular rotatingblades having a plurality of teeth disposed along the perimetrical edgeof the blade. For a jointer or planer, the cutting tool typicallyincludes a plurality of radially spaced-apart blades. For a band saw,the cutting tool includes an elongate, circuitous tooth-edged band.

Safety system 18 includes a detection subsystem 22, a reaction subsystem24 and a control subsystem 26. Control subsystem 26 may be adapted toreceive inputs from a variety of sources including detection subsystem22, reaction subsystem 24, operative structure 12 and motor assembly 16.The control subsystem may also include one or more sensors adapted tomonitor selected parameters of machine 10. In addition, controlsubsystem 26 typically includes one or more instruments operable by auser to control the machine. The control subsystem is configured tocontrol machine 10 in response to the inputs it receives.

Detection subsystem 22 is configured to detect one or more dangerous, ortriggering, conditions during use of machine 10. For example, thedetection subsystem may be configured to detect that a portion of theuser's body is dangerously close to, or in contact with, a portion ofcutting tool 14. As another example, the detection subsystem may beconfigured to detect the rapid movement of a workpiece due to kickbackby the cutting tool, as is described in U.S. Provisional PatentApplication Ser. Nos. 60/182,866, the disclosure of which is hereinincorporated by reference. In some embodiments, detection subsystem 22may inform control subsystem 26 of the dangerous condition, which thenactivates reaction subsystem 24. In other embodiments, the detectionsubsystem may be adapted to activate the reaction subsystem directly.

Once activated in response to a dangerous condition, reaction subsystem24 is configured to engage operative structure 12 quickly to preventserious injury to the user. It will be appreciated that the particularaction to be taken by reaction subsystem 24 will vary depending on thetype of machine 10 and/or the dangerous condition that is detected. Forexample, reaction subsystem 24 may be configured to do one or more ofthe following: stop the movement of cutting tool 14, disconnect motorassembly 16 from power source 20, place a barrier between the cuttingtool and the user, or retract the cutting tool from its operatingposition, etc. The reaction subsystem may be configured to take acombination of steps to protect the user from serious injury. Placementof a barrier between the cutting tool and teeth is described in moredetail in U.S. Provisional Patent Application Ser. No. 60/225,206,entitled “Cutting Tool Safety System,” filed Aug. 14, 2000 by SD3, LLC,the disclosure of which is herein incorporated by reference. Retractionof the cutting tool from its operating position is described in moredetail in U.S. Provisional Patent Application Ser. No. 60/225,089,entitled “Retraction System For Use In Power Equipment,” filed Aug. 14,2000 by SD3, LLC, the disclosure of which is herein incorporated byreference.

The configuration of reaction subsystem 24 typically will vary dependingon which action(s) are taken. In the exemplary embodiment depicted inFIG. 1, reaction subsystem 24 is configured to stop the movement ofcutting tool 14 and includes a brake mechanism 28, a biasing mechanism30, a restraining mechanism 32, and a release mechanism 34. Brakemechanism 28 is adapted to engage operative structure 12 under theurging of biasing mechanism 30. During normal operation of machine 10,restraining mechanism 32 holds the brake mechanism out of engagementwith the operative structure. However, upon receipt of an activationsignal by reaction subsystem 24, the brake mechanism is released fromthe restraining mechanism by release mechanism 34, whereupon, the brakemechanism quickly engages at least a portion of the operative structureto bring the cutting tool to a stop.

It will be appreciated by those of skill in the art that the exemplaryembodiment depicted in FIG. 1 and described above may be implemented ina variety of ways depending on the type and configuration of operativestructure 12. Turning attention to FIG. 2, one example of the manypossible implementations of safety system 18 is shown. System 18 isconfigured to engage an operative structure having a cutting tool in theform of a circular blade 40 mounted on a rotating shaft or arbor 42.Blade 40 includes a plurality of cutting teeth (not shown) disposedaround the outer edge of the blade. As described in more detail below,braking mechanism 28 is adapted to engage the teeth of blade 40 and stopthe rotation of the blade. U.S. Provisional Patent Application Ser. No.60/225,210, entitled “Translation Stop For Use In Power Equipment,”filed Aug. 14, 2000 by SD3, LLC, the disclosure of which is hereinincorporated by reference, describes other systems for stopping themovement of the cutting tool. U.S. Provisional Patent Application Ser.No. 60/225,057, entitled “Miter Saw With Improved Safety System,” filedAug. 14, 2000 by SD3, LLC, the disclosure of which is hereinincorporated by reference, describes safety system 18 in the context ofparticular types of machines 10.

In the exemplary implementation, detection subsystem 22 is adapted todetect the dangerous condition of the user coming into contact withblade 40. The detection subsystem includes a sensor assembly, such ascontact detection plates 44 and 46, capacitively coupled to blade 40 todetect any contact between the user's body and the blade. Typically, theblade, or some larger portion of cutting tool 14 is electricallyisolated from the remainder of machine 10. Alternatively, detectionsubsystem 22 may include a different sensor assembly configured todetect contact in other ways, such as optically, resistively, etc. Inany event, the detection subsystem is adapted to transmit a signal tocontrol subsystem 26 when contact between the user and the blade isdetected. Various exemplary embodiments and implementations of detectionsubsystem 22 are described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,200, entitled “Contact Detection System ForPower Equipment,” filed Aug. 14, 2000 by SD3, LLC, and U.S. ProvisionalPatent Application Ser. No. 60/225,211, entitled “Apparatus And MethodFor Detecting Dangerous Conditions In Power Equipment,” filed Aug. 14,2000 by SD3, LLC, the disclosures of which are herein incorporated byreference.

Control subsystem 26 includes one or more instruments 48 that areoperable by a user to control the motion of blade 40. Instruments 48 mayinclude start/stop switches, speed controls, direction controls, etc.Control subsystem 26 also includes a logic controller 50 connected toreceive the user's inputs via instruments 48. Logic controller 50 isalso connected to receive a contact detection signal from detectionsubsystem 22. Further, the logic controller may be configured to receiveinputs from other sources (not shown) such as blade motion sensors,workpiece sensors, etc. In any event, the logic controller is configuredto control operative structure 12 in response to the user's inputsthrough instruments 48. However, upon receipt of a contact detectionsignal from detection subsystem 22, the logic controller overrides thecontrol inputs from the user and activates reaction subsystem 24 to stopthe motion of the blade. Various exemplary embodiments andimplementations of control subsystem 26 are described in more detail inU.S. Provisional Patent Application Ser. No. 60/225,059, entitled “LogicControl For Fast Acting Safety System,” filed Aug. 14, 2000 by SD3, LLC,and U.S. Provisional Patent Application Ser. No. 60/225,094, entitled“Motion Detecting System For Use In Safety System For Power Equipment,”filed Aug. 14, 2000 by SD3, LLC, the disclosures of which are hereinincorporated by reference.

In the exemplary implementation, brake mechanism 28 includes a pawl 60mounted adjacent the edge of blade 40 and selectively moveable to engageand grip the teeth of the blade. Pawl 60 may be constructed of anysuitable material adapted to engage and stop the blade. As one example,the pawl may be constructed of a relatively high strength thermoplasticmaterial such as polycarbonate, ultrahigh molecular weight polyethylene(UHMW) or Acrylonitrile Butadiene Styrene (ABS), etc., or a metal suchas aluminum, etc. It will be appreciated that the construction of pawl60 will vary depending on the configuration of blade 40. In any event,the pawl is urged into the blade by a biasing mechanism in the form of aspring 66. In the illustrative embodiment shown in FIG. 2, pawl 60 ispivoted into the teeth of blade 40. It should be understood that slidingor rotary movement of pawl 60 might also be used. The spring is adaptedto urge pawl 60 into the teeth of the blade with sufficient force togrip the blade and quickly bring it to a stop.

The pawl is held away from the edge of the blade by a restrainingmechanism the form of a fusible member 70. The fusible member isconstructed of a suitable material adapted to restrain the pawl againstthe bias of spring 66, and also adapted to melt under a determinedelectrical current density. Examples of suitable materials for fusiblemember 70 include NiChrome wire, stainless steel wire, etc. The fusiblemember is connected between the pawl and a contact mount 72. Preferably,fusible member 70 holds the pawl relatively close to the edge of theblade to reduce the distance the pawl must travel to engage the blade.Positioning the pawl relatively close to the edge of the blade reducesthe time required for the pawl to engage and stop the blade. Typically,the pawl is held approximately 1/32-inch to ¼-inch from the edge of theblade by fusible member 70, however other pawl-to-blade spacings mayalso be used within the scope of the invention.

Pawl 60 is released from its unactuated, or cocked, position to engageblade 40 by a release mechanism in the form of a firing subsystem 76.The firing subsystem is coupled to contact mount 72, and is configuredto melt fusible member 70 by passing a surge of electrical currentthrough the fusible member. Firing subsystem 76 is coupled to logiccontroller 50 and activated by a signal from the logic controller. Whenthe logic controller receives a contact detection signal from detectionsubsystem 22, the logic controller sends an activation signal to firingsubsystem 76, which melts fusible member 70, thereby releasing the pawlto stop the blade. Various exemplary embodiments and implementations ofreaction subsystem 24 are described in more detail in U.S. ProvisionalPatent Application Ser. No. 60/225,056, entitled “Firing Subsystem ForUse In Fast Acting Safety System,” filed Aug. 14, 2000 by SD3, LLC, U.S.Provisional Patent Application Ser. No. 60/225,170, entitled“Spring-Biased Brake Mechanism for Power Equipment,” filed Aug. 14, 2000by SD3, LLC, and U.S. Provisional Patent Application Ser. No.60/225,169, entitled “Brake Mechanism For Power Equipment,” filed Aug.14, 2000 by SD3, LLC, the disclosures of which are herein incorporatedby reference.

It will be appreciated that activation of the brake mechanism willrequire the replacement of one or more portions of safety system 18. Forexample, pawl 60 and fusible member 70 typically must be replaced beforethe safety system is ready to be used again. Thus, it may be desirableto construct one or more portions of safety system 18 in a cartridgethat can be easily replaced. For example, in the exemplaryimplementation depicted in FIG. 2, safety system 18 includes areplaceable cartridge 80 having a housing 82. Pawl 60, spring 66,fusible member 70 and contact mount 72 are all mounted within housing82. Alternatively, other portions of safety system 18 may be mountedwithin the housing. In any event, after the reaction system has beenactivated, the safety system can be reset by replacing cartridge 80. Theportions of safety system 18 not mounted within the cartridge may bereplaced separately or reused as appropriate. Various exemplaryembodiments and implementations of a safety system using a replaceablecartridge are described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,201, entitled “Replaceable Brake MechanismFor Power Equipment,” filed Aug. 14, 2000 by SD3, LLC, and U.S.Provisional Patent Application Ser. No. 60/225,212, entitled “BrakePositioning System,” filed Aug. 14, 2000 by SD3, LLC, the disclosures ofwhich are herein incorporated by reference.

While one particular implementation of safety system 18 has beendescribed, it will be appreciated that many variations and modificationsare possible within the scope of the invention. Many such variations andmodifications are described in U.S. Provisional Patent Application Ser.Nos. 60/182,866 and 60/157,340, the disclosures of which are hereinincorporated by reference.

FIG. 3 shows one type of a table saw 1400, often called a contractor'ssaw. It includes a table 1401 through which a blade 1402 extends frombeneath the table. The table and blade are supported by a housing 1403and legs 1404. Housing 1403 encloses the mechanics that support,position and drive the blade. A motor to drive the blade can bepositioned in or outside of the housing. A switch 1405 turns the saw onand off, causing blade 1402 to spin. Handles, such as handle 1406, areused to adjust the position of the blade relative to the table, forexample, how far the blade extends above the table or how the bladetilts relative to the top of the table. Of course, table saws take manydifferent configurations, from large saws sized for industrial use tosmall saws that can be placed on a bench top or counter, and table sawscome with various types of tables and housings. Essentially, a table sawis a saw with a flat workspace or “table” and a cutting blade projectingup through the table. A user places a workpiece on the table and slidesit into the blade to cut the workpiece.

FIGS. 4 and 5 show side elevation views of the internal mechanism onetype of table saw configured with a safety system as described above.FIG. 6 shows a bottom view of the same saw, and FIG. 7 shows aperspective view.

In the saw, blade 1402 is mounted on an arbor 1407 by a nut (not shown).The arbor spins the blade in the direction of arrow 1409. Table 1401(not shown in FIG. 5), which defines the work surface for the table saw,is adjacent the blade and the blade extends above the table.

An arbor block 1410 supports arbor 1407 and holds the arbor in bearingsto allow the arbor to rotate. The arbor is connected to a motor (notshown), such as by belt extending around a pulley on the arbor and apulley on the motor's drive shaft, and the motor drives or spins thearbor, as is known in the art. The motor may be mounted on motor plate1411 shown in FIG. 5.

Arbor block 1410 is also mounted on a pin 1412 and may pivot around thatpin. Pin 1412, in turn, is mounted to a support member 1413 that, alongwith another support member 1414, comprise at least part of thesupporting frame of the table saw. The supporting frame is connected tothe housing, legs, and/or table.

Blade 1402 is configured to pivot up and down so that a user canposition the blade to extend above the table as needed. The blade pivotsaround pin 1412. A user may pivot the blade to adjust its position byturning a shaft 1415 on which a worm gear 1416 is mounted. The worm gearis mounted on the shaft so that it turns with the shaft, but so that itmay slide on the shaft when necessary, as explained below. Worm gear1416 is mounted on shaft 1415 like a collar, with the shaft extendingthrough a longitudinal hole in the worm gear. The worm gear is held inplace during normal operation of the saw by a spring clip 1417, which ispositioned in a notch or channel on the worm gear and which also engagesa detent or groove on shaft 1415 to hold the worm gear in place. Theworm gear engages a rack or segment gear 1418 that is connected to orpart of arbor block 1410. Thus, when a user turns shaft 1415, such as byturning a knob or handle attached to the shaft, like handle 1406 in FIG.3, worm gear 1416 moves rack 1418 and the blade up and down, dependingon the direction that the worm gear is turned.

Most table saws are also configured to allow blade 1402 to tilt fromside to side relative to table 1401. That is accomplished by a systemsimilar to shaft 1415, worm gear 1416, and rack 1418, but orientedgenerally perpendicularly to the plane of the blade. Support members1413 and 1414 may be used as part of that system; for example, supportmember 1414 may comprise a segment gear or rack like rack 1418. Thesupport members include arcuate projections 1440 that fit into arcuategrooves or slides in mounting blocks (not shown) to allow the supportmembers to pivot. The mounting blocks are secured to the table of thesaw.

A brake cartridge 1419 is mounted in the saw adjacent blade 1402. (Thecartridge is shown open in FIGS. 4 and 6, and shown with a cover in FIG.7.) The cartridge may be configured as described above and as describedin more detail in U.S. Provisional Patent Application Ser. No.60/225,201, titled “Replaceable Brake Mechanism for Power Equipment,”and U.S. Provisional Patent Application Ser. No. 60/225,212, titled“Brake Positioning System,” both filed Aug. 14, 2000. The brakecartridge includes a pawl 1420 biased toward blade 1402 by a spring1421. Various pawls are described in more detail in U.S. ProvisionalPatent Application Ser. No. 60/225,169, titled “Brake Mechanism forPower Equipment,” filed Aug. 14, 2000. The pawl is held away from blade1402 by a release mechanism 1422, as described generally above and asdescribed in more detail in U.S. Provisional Patent Application Ser. No.60/225,170, titled “Spring-Biased Brake Mechanism for Power Equipment,”filed Aug. 14, 2000. The cartridge is configured so that the releasemechanism releases the pawl into the blade upon the receipt of adetection signal, as explained generally above and as explained in moredetail in U.S. Provisional Patent Application Ser. No. 60/225,056,titled “Firing Subsystem for use in a Fast-Acting Safety System,” filedAug. 14, 2000. The detection signal that causes the release of the pawl,and the system or systems to generate that signal, are explained in moredetail in U.S. Provisional Patent Application Ser. No. 60/225,200,titled “Contact Detection System for Power Equipment,” and U.S.Provisional Patent Application Ser. No. 60/225,211, titled “Apparatusand Method for Detecting Dangerous Conditions in Power Equipment,” bothfiled Aug. 14, 2000. Electronics that form at least part of the systemto detect contact between a user and the blade, and then to signal therelease of the brake pawl, are enclosed in housing 1423 mounted on arborblock 1410. The housing should be closed to prevent sawdust and otherparticles from entering the housing and potentially damaging theelectronics housed therein.

When the pawl is released, the pawl quickly hits the teeth of the blade.The teeth bite into the pawl, stopping the blade. The saw describedabove can stop the blade in 2-10 milliseconds, thereby reducing theextent of injury caused by accidental contact with the blade.

Brake cartridge 1419 is positioned on the blade's pivot axis so thatpawl 1420 can move around pin 1412. Thus, when pawl 1420 hits the blade,the angular momentum of the blade is transferred to the arbor, and theblade, arbor, rack and cartridge tend to retract or move down in thedirection of arrow 1424. The blade will move down to the extentpermitted by the contact between rack 1418 and worm gear 1416. If theworm gear is fixed in place, the downward movement of the blade maystrip teeth on the rack and/or worm gear, and may prevent the blade frommoving down as far as desired. In the embodiment shown in FIGS. 4 and 5,the worm gear is adapted to snap free and move on shaft 1415 when theblade hits the pawl.

When the blade hits the pawl, the force of the impact causes spring clip1417 to snap loose, allowing the worm gear to slide down shaft 1415toward an end 1425 of the shaft. The spring clip snaps loose because therack is urged down when the blade is stopped, and the rack contacts theworm gear and forces the worm gear to move. The force of the rackagainst the worm gear causes the spring clip to snap loose. The wormgear then moves into a receptacle 1426 formed around the end of theshaft. The worm gear is put back in place by simply raising arbor 1410up, or by rotating shaft 1415 to pivot the blade up, which causes therack to move up and the worm gear to slide back along shaft 1415 untilthe spring clip snaps into place on the shaft.

The table saw shown in FIGS. 4 and 5 also includes a support 1427configured with a seat or region 1428 in which is placed animpact-absorbing material 1429 (shown in FIGS. 4 and 5, but not in FIG.7). The support is positioned under the arbor and arbor block so thatwhen the blade retracts, the arbor block strikes impact-absorbingmaterial 1429. Support 1427 and impact-absorbing material 1429 act as abarrier to stop the downward movement of the blade. The support ispositioned so that blade 1402 may retract a sufficient distance. Theimpact-absorbing material can be any one of a number of cushioningmaterials, such as rubber, dense foam, plastic, etc. Alternatively,impact-absorbing material 1429 may be attached to the undersurface ofthe arbor block instead of on support 1427. Additionally, support 1427may take many forms. In fact, shaft 1415 may be configured andpositioned so that it provides a surface to stop the downward movementof the blade.

In the construction described above, the angular momentum of the bladecauses the blade, rack and cartridge to all pivot down when the pawlstrikes the blade. Thus, the angular momentum of the blade causes theretraction. Blade 1402 is permitted to move downward a sufficientdistant so that the blade is completely retracted. The ability of theblade to retract minimizes any injury from accidental contact with theblade and works simultaneously with the braking system described above.The ability of the blade to retract is in part because the point aroundwhich the blade pivots relative to the direction that the blade spinsmay be described as on what could be thought of as the “back side” ofexisting table saws. The brake cartridge is also mounted on this “backside,” and may be mounted to pivot with the blade as described above, ormay be fixedly mounted to the frame of the saw so it does not pivot withthe blade and so that the blade climbs down the pawl when the pawlengages the blade. Other configurations to cause the blade to retract,which can be used alone or in conjunction with the embodiment describedherein, are described in U.S. Provisional Patent Application Ser. No.60/225,089, titled “Retraction System for Use in Power Equipment,” filedAug. 14, 2000.

FIG. 5 also shows a splitter 1430 that extends above table 1401 behindblade 1402 to prevent kickback. A blade guard may also substantiallyenclose blade 1402 and prevent accidental contact with the blade.

Table saws like those described above can include logic controls to testthat the saw and its safety system are functioning properly. Forexample, the logic controls can verify that the brake pawl is in placeadjacent the blade, and that the firing system is ready to release thepawl into the blade upon the detection of accidental contact between theblade and a user. The saws also may include various signals, lights,etc., to inform a user of the status of the saw and the features inoperation. Self tests, logic controls and user interfaces are describedin more detail in U.S. Provisional Patent Application Ser. No.60/225,059, titled “Logic Control for Fast Acting Safety System,” andU.S. Provisional Patent Application Ser. No. 60/225,094, titled “MotionDetecting System for Use in Safety System for Power Equipment,” bothfiled Aug. 14, 2000.

The table saws described above are configured to absorb the impact of abrake pawl stopping a blade. However, on some table saws, small saws forexample, it may be desirable to construct the saw knowing that if thebrake pawl stops the blade, the saw would be damaged, perhaps by bendingthe arbor or other support structure. In fact, the saw may beconstructed specifically to absorb the energy of stopping the blade bydestroying or damaging part of the saw. Such saws may be thought of asdisposable to the extent they are intended to be used only until anaccident occurs requiring the brake pawl to stop the blade. A disposablesaw may be less expensive to manufacture, and reduced injury to a userin the event of an accident would more than justify the entire cost ofthe saw.

INDUSTRIAL APPLICABILITY

The present invention is applicable to power equipment, and specificallyto table saws.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. No single feature,function, element or property of the disclosed embodiments is essentialto all of the disclosed inventions. Similarly, where the claims recite“a” or “a first” element or the equivalent thereof, such claims shouldbe understood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and subcombinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and subcombinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. A table saw comprising: a frame including a table defining a worksurface; an arbor block supported by the frame; a bearing supported bythe arbor block; a rotatable arbor supported by the bearing; a blademounted on the arbor and extendable up through the work surface; anadjustment mechanism configured to adjust the position of the bladerelative to the table; a detection system configured to detect adangerous condition between a person and the blade; and a brakeconfigured to engage and stop the blade upon detection of the dangerouscondition between the person and the blade; where the brake is mountedto the arbor block to maintain an operative position relative to theblade as the position of the blade is adjusted.
 2. The table saw ofclaim 1, where the adjustment mechanism is configured to adjust thevertical position of the blade relative to the table.
 3. The table sawof either of claim 1, where the adjustment mechanism is configured toadjust the angular position of the blade relative to the table.
 4. Thetable saw of claim 1, where the blade is coupled to the frame by asupport structure that is selectively positionable relative to theframe, and where the brake is coupled to the support structure.
 5. Thetable saw of claim 1, where the blade includes a perimeter and a cuttingedge around its perimeter, where the brake is configured to engage thecutting edge of the blade to stop the blade upon detection of thedangerous condition between the person and the blade, and where theoperative position of the brake is adjacent the cutting edge of theblade.
 6. The table saw of claim 5, where the adjustment mechanism isconfigured to tilt the blade relative to the table.
 7. The table saw ofclaim 6, where the adjustment mechanism is configured to change theelevation of the blade relative to the table.
 8. The table saw of claim1, where the arbor block supports the brake when the brake engages theblade.
 9. A table saw comprising: a table defining a work surface; arotatable blade extendable up through the work surface; an elevationmechanism adapted to change the elevation of the blade relative to thetable; a detection system adapted to detect a dangerous conditionbetween a person and the blade; and a brake adapted to engage anddecelerate the blade when the detection system detects the dangerouscondition between the person and the blade, where the brake changeselevation relative to the table by pivoting when the elevation mechanismchanges the elevation of the blade relative to the table.
 10. The tablesaw of claim 9 where the elevation mechanism is adapted to change theelevation of the blade by pivoting the blade up and down.
 11. The tablesaw of claim 9 where changing the elevation of the blade changes theelevation of the brake.
 12. The table saw of claim 9 where the elevationmechanism is adapted to change the elevation of the blade by pivotingthe blade up and down and where pivoting the blade up and down changesthe elevation of the brake.
 13. The table saw of claim 9 where theelevation mechanism is adapted to change the elevation of the blade bypivoting the blade up and down and where pivoting the blade up and downpivots the brake up and down.
 14. The table saw of claim 9 where theelevation mechanism includes an arbor block adapted to pivot around apin, and further comprising a brake positioning mechanism adapted tomount the brake to the arbor block so the brake moves pivots with thearbor block.
 15. The table saw of claim 9 where the dangerous conditionis contact between a person and the blade.
 16. The table saw of claim 9where the dangerous condition is proximity between a person and theblade.
 17. A table saw comprising: a frame including a table defining awork surface; a rotatable blade coupled to the frame and extendable upthrough the work surface; an elevation mechanism adapted to change theelevation of the blade relative to the table; a detection system adaptedto detect a dangerous condition between a person and the blade; and abrake adapted to decelerate the blade upon detection of the dangerouscondition; and brake positioning means for pivoting the brake up anddown to maintain the brake in an operative position relative to theblade as the elevation of the blade relative to the table is changed.18. The table saw of claim 17 where the dangerous condition is contactbetween a person and the blade.
 19. The table saw of claim 17 where thedangerous condition is proximity between a person and the blade.